# JWST Observations of the Enigmatic Y Dwarf WISE 1828+2650: I. Limits to a Binary Companion

## TL;DR

This study uses JWST and Keck observations to investigate whether the cold Y dwarf WISE 1828+2650 has a binary companion, finding no evidence for multiplicity beyond 0.5 AU, which impacts models of its physical characteristics.

## Contribution

The paper provides new high-resolution imaging data that constrains the presence of a binary companion to WISE 1828+2650, refining understanding of its nature and aiding future spectral modeling.

## Key findings

- No evidence for a binary companion beyond 0.5 AU from JWST and Keck data.
- New photometry from JWST in 6 filters for improved model fitting.
- Constraints on the multiplicity of the Y dwarf WISE 1828+2650.

## Abstract

The Y-dwarf WISE 1828+2650 is one of the coldest known Brown Dwarfs with an effective temperature of $\sim$300 K. Located at a distance of just 10 pc, previous model-based estimates suggest WISE1828+2650 has a mass of $\sim$5-10 Mj, making it a valuable laboratory for understanding the formation, evolution and physical characteristics of gas giant planets. However, previous photometry and spectroscopy have presented a puzzle with the near-impossibility of simultaneously fitting both the short (0.9-2.0 microns) and long wavelength (3-5 microns) data. A potential solution to this problem has been the suggestion that WISE 1828+2650 is a binary system whose composite spectrum might provide a better match to the data. Alternatively, new models being developed to fit JWST/NIRSpec and MIRI spectroscopy might provide new insights. This article describes JWST/NIRCam observations of WISE 1828+2650 in 6 filters to address the binarity question and to provide new photometry to be used in model fitting. We also report Adaptive Optics imaging with the Keck 10 m telescope. We find no evidence for multiplicity for a companion beyond 0.5 AU with either JWST or Keck. Companion articles will present low and high resolution spectra of WISE 1828+2650 obtained with both NIRSpec and MIRI.